当我通过导航抽屉点击导航抽屉呼叫第二个活动时，应用程序停止工作

时间：2015-03-30 20:41:19

标签： java android listview navigation-drawer soundpool

好的，我想让导航抽屉可用于所有活动。我正在创建一个音板应用程序，当我点击列表中的项目0时，我希望它带我到第一个有导航抽屉和第一个音板活动的活动。从那个活动开始，我想打开导航抽屉并点击列表上的另一个项目，它可以带我进入带有音板的活动等等......当应用程序打开时，我的导航抽屉工作正常我点击位置0，它将我带到另一个活动，应用程序中的音板关闭，因为它已停止工作。我做错了什么？我该如何纠正它才能发挥作用。

这是我在启动应用时打开的主要活动代码：

public class MainActivity extends ActionBarActivity {

DrawerLayout mDrawerLayout;
ListView mDrawerList;
ActionBarDrawerToggle mDrawerToggle;
String[] mDrawerListItems;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar)findViewById(R.id.toolbar);
    mDrawerLayout = (DrawerLayout)findViewById(R.id.drawer);
    mDrawerList = (ListView)findViewById(android.R.id.list);
    mDrawerListItems = getResources().getStringArray(R.array.drawer_list);
    mDrawerList.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, mDrawerListItems));
    mDrawerList.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            switch(position) {
                case 0:
                    Intent i = new Intent(MainActivity.this, MrsClubb.class);
                    startActivity(i);
            }
            mDrawerLayout.closeDrawer(mDrawerList);

        }
    });
    mDrawerToggle = new ActionBarDrawerToggle(this,
            mDrawerLayout,
            toolbar,
            R.string.drawer_open,
            R.string.drawer_close){
        public void onDrawerClosed(View v){
            super.onDrawerClosed(v);
            invalidateOptionsMenu();
            syncState();
        }
        public void onDrawerOpened(View v){
            super.onDrawerOpened(v);
            invalidateOptionsMenu();
            syncState();
        }
    };
    mDrawerLayout.setDrawerListener(mDrawerToggle);
    setSupportActionBar(toolbar);
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    getSupportActionBar().setHomeButtonEnabled(true);
    mDrawerToggle.syncState();
}

@Override
protected void onPostCreate(Bundle savedInstanceState){
    super.onPostCreate(savedInstanceState);
    mDrawerToggle.syncState();
}

@Override
public void onConfigurationChanged(Configuration newConfig){
    super.onConfigurationChanged(newConfig);
    mDrawerToggle.onConfigurationChanged(newConfig);
}

@Override
public boolean onOptionsItemSelected(MenuItem item){
    switch (item.getItemId()){
        case android.R.id.home: {
            if (mDrawerLayout.isDrawerOpen(mDrawerList)){
                mDrawerLayout.closeDrawer(mDrawerList);
            } else {
                mDrawerLayout.openDrawer(mDrawerList);
            }
            return true;
        }
        default: return super.onOptionsItemSelected(item);
    }
}
}

这是我的第二堂课，我希望列表视图中的位置0能够将我带到音板中：

public class MrsClubb extends ActionBarActivity {

DrawerLayout mDrawerLayout;
ListView mDrawerList;
ActionBarDrawerToggle mDrawerToggle;
String[] mDrawerListItems;



SoundPool Clubb1;
int clubb1Id;




@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.mrsclubb);
Clubb1 = new SoundPool(10, AudioManager.STREAM_MUSIC, 1);
clubb1Id = Clubb1.load(this, R.raw.clubb1,1);


    Toolbar toolbar = (Toolbar)findViewById(R.id.toolbar);
    mDrawerLayout = (DrawerLayout)findViewById(R.id.drawer);
    mDrawerList = (ListView)findViewById(android.R.id.list);
    mDrawerListItems = getResources().getStringArray(R.array.drawer_list);
    mDrawerList.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, mDrawerListItems));
    mDrawerList.setOnItemClickListener(new AdapterView.OnItemClickListener()
    {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            switch(position) {
                case 0:
                    Intent i = new Intent(MrsClubb.this, MrsClubb.class);
                    startActivity(i);
            }
            mDrawerLayout.closeDrawer(mDrawerList);

        }
    });
    mDrawerToggle = new ActionBarDrawerToggle(this,
            mDrawerLayout,
            toolbar,
            R.string.drawer_open,
            R.string.drawer_close){
        public void onDrawerClosed(View v){
            super.onDrawerClosed(v);
            invalidateOptionsMenu();
            syncState();
        }
        public void onDrawerOpened(View v){
            super.onDrawerOpened(v);
            invalidateOptionsMenu();
            syncState();
        }
    };
    mDrawerLayout.setDrawerListener(mDrawerToggle);
    setSupportActionBar(toolbar);
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    getSupportActionBar().setHomeButtonEnabled(true);
    mDrawerToggle.syncState();
}

@Override
protected void onPostCreate(Bundle savedInstanceState){
    super.onPostCreate(savedInstanceState);
    mDrawerToggle.syncState();
}

@Override
public void onConfigurationChanged(Configuration newConfig){
    super.onConfigurationChanged(newConfig);
    mDrawerToggle.onConfigurationChanged(newConfig);
}

@Override
public boolean onOptionsItemSelected(MenuItem item){
    switch (item.getItemId()){
        case android.R.id.home: {
            if (mDrawerLayout.isDrawerOpen(mDrawerList)){
                mDrawerLayout.closeDrawer(mDrawerList);
            } else {
                mDrawerLayout.openDrawer(mDrawerList);
            }
            return true;
        }
        default: return super.onOptionsItemSelected(item);
    }
} public void playSound1(View view) {Clubb1.play(clubb1Id, 1, 1, 1, 0, 1);}

}

这是清单：

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name=".MainActivity"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity
        android:name=".MrsClubb"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MRSCLUBB" />

            <category android:name="android.intent.category.DEFAULT" />
        </intent-filter>
    </activity>
</application>

这是LogCat：

-30 21:58:33.984 1971-1971/com.jonatboard.jonat.htssoundboard D/AndroidRuntime﹕ Shutting
down VM
 --------- beginning of crash
03-30 21:58:33.985 1971-1971/com.jonatboard.jonat.htssoundboard E/AndroidRuntime﹕
FATAL EXCEPTION: main
 Process: com.jonatboard.jonat.htssoundboard, PID: 1971
 java.lang.RuntimeException: Unable to start activity
ComponentInfo{com.jonatboard.jonat.htssoundboard/com.jonatboard.jonat.htssoundboard.MrsClu
bb}: java.lang.NullPointerException: Attempt to invoke virtual method 'void
android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
 at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
 at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
 at android.app.ActivityThread.access$800(ActivityThread.java:144)
 at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
 at android.os.Handler.dispatchMessage(Handler.java:102)
 at android.os.Looper.loop(Looper.java:135)
 at android.app.ActivityThread.main(ActivityThread.java:5221)
 at java.lang.reflect.Method.invoke(Native Method)
 at java.lang.reflect.Method.invoke(Method.java:372)
 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
 Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void
android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
 at com.jonatboard.jonat.htssoundboard.MrsClubb.onCreate(MrsClubb.java:49)
 at android.app.Activity.performCreate(Activity.java:5933)
 at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
 at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
 at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
 at android.app.ActivityThread.access$800(ActivityThread.java:144)
 at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
 at android.os.Handler.dispatchMessage(Handler.java:102)
 at android.os.Looper.loop(Looper.java:135)
 at android.app.ActivityThread.main(ActivityThread.java:5221)
 at java.lang.reflect.Method.invoke(Native Method)
 at java.lang.reflect.Method.invoke(Method.java:372)
 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

如果您需要更多代码，请告诉我们，我们非常感谢您的帮助。

2 个答案:

答案 0 :(得分：0)

这是你的问题：

 java.lang.NullPointerException: Attempt to invoke virtual method 'void
android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference

看起来您的listView为空，请检查以确保您在活动中声明并正确查找。

答案 1 :(得分：0)

你的问题是在MrsClubb活动中错误地引用DrawerLayout中的ListView。以下是您应该如何使用和引用ListView的示例。

<android.support.v4.widget.DrawerLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <FrameLayout
        android:id="@+id/content"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>
    <ListView
        android:id="@+id/drawer"
        android:layout_width="240dp"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:background="#111"
        android:choiceMode="singleChoice"
        android:divider="@android:color/transparent"
        android:dividerHeight="0dp"/>
</android.support.v4.widget.DrawerLayout>

现在您可以将DrawerLayout中的ListView引用为：

ListView lv = (ListView) findViewByid(R.id.drawer);

使用Android提供的ID有时会变得棘手，我相信这是你出错的地方。

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